Modulation of prostaglandin E2-induced Ca2+ influx by steroid hormones in osteoblast-like cells

In osteoblast-like MC3T3-E1 cells, we previously reported that prostaglandin E2 (PGE2), a potent bone resorbing agent, stimulates Ca2+ influx (H. Tokuda, M. Miwa, Y. Oiso and O. Kozawa, Cell Signal 1992; 4: 261-266). In this study, we examined the effects of various hormones belonging to the steroid hormone superfamily on PGE2-induced Ca2+ influx in MC3T-E1 cells. 1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3], an active form of vitamin D3, dexamethasone and retinoic acid significantly inhibited the PGE2-induced Ca2+ influx in a dose-dependent manner in these cells. The effects of these hormones were dependent on the time of pretreatment and submaximum inhibitions were observed at 6 h. In contrast, 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3], an inactive form of vitamin D3, 17 beta-estradiol, progesterone, testosterone and triiodothyronine had little effect on the PGE2-induced Ca2+ influx in these cells. These results suggest that, in the steroid hormone superfamily, 1,25-dihydroxyvitamin D3, glucocorticoid and retinoic acid modulate bone metabolism through the inhibition of Ca2+ influx induced by PGE2 in osteoblast-like cells.